146 LIFE AND HER CHILDREN. 
usual food, though they by no means despise warm- 
blooded animals when they get a chance to fasten 
upon them. 
The elastic-ringed animals are not, however, con- 
fined to fresh water ; on the contrary, though they 
cannot breathe in perfectly dry air, yet they have 
found their way underground in the common earth- 
worm, and there are many of them in the sea, from 
which probably they first came, and where they are 
protected and armed in many very curious ways. 
The common earthworm, which we all know so 
well, is a curious example of a water-animal adapted 
to live under the earth. He breathes as the leech 
does, and he must have moisture, for perfectly dry air 
is useless to him, and he dies quickly in very dry 
places where he cannot keep his body moistened 
with slime. Eyes would be of no use in his under- 
ground journeys, and he only comes above ground 
at night, so we find that these organs are wanting ; 
suckers too would be a hindrance to him, and his 
body ends in a fine tapering point which he can push 
into the earth like a shoemaker's awl. 
But how is he to force his way through the earth ? 
If you pass your hand along his body from the tail 
to the head you will feel a gentle resistance, for 
every ring bears four pair of hooked bristles pointing 
backwards, so fine as not to be easily seen, but strong 
enough for his work. When he has pushed the front 
part of his body a little way into the earth he then 
draws it up by shortening the long muscles, and the 
bristles make no resistance because they point towards 
the tail ; then he contracts his ring muscles and so 
forces his body to lengthen again, but this time it 
